docs: def pip_install(package, fatal=False, upgrade=False, venv=None,
                  constraints=None, **options):
      """Install a python package"""
      if venv:
          venv_python = os.path.join(venv, 'bin/pip')
          command = [venv_python, "install"]
      else:
          command = ["install"]
  
      available_options = ('proxy', 'src', 'log', 'index-url', )
      for option in parse_options(options, available_options):
          command.append(option)
  
      if upgrade:
          command.append('--upgrade')
  
      if constraints:
          command.extend(['-c', constraints])
  
      if isinstance(package, list):
          command.extend(package)
      else:
          command.append(package)
  
      log("Installing {} package with options: {}".format(package,
                                                          command))
      if venv:
          subprocess.check_call(command)
      else:
          pip_execute(command)